Toward a phylogeny of the thelodonts

We investigated the phylogenetic relationships of thelodonts by compiling data on 25 species in 15 genera, comprising most of the known thelodonts represented by articulated specimens (squamations), together with four outgroup taxa. Character states for 53 characters (83 apomorphic states) were compiled and analyzed using Maximum Parsimony methods to yield 150 shortest trees of 177 steps each. The consensus summary of these trees was judged to be unreliable owing to the uncertain placement of two "wild-card" taxa (one of which was an outgroup). After removal of these two taxa a second analysis yielded 31 shortest trees of 153 steps. The consensus tree suggests a monophyletic Thelodonti in which a basal split separates Phlebolepis plus Erepsilepis and their sister Archipelepis from the remaining taxa. Within the remaining species, a group consisting of Turinia plus Loganellia and their possible sister Phillipsilepis is collectively sister to Shielia plus Lanarkia and their sister the Furcacaudiformes. The latter group is monophyletic and comprises the basal Pezopallichthys and a monophyletic Furcacaudidae. These results must be considered tentative pending addition of new characters and inclusion of data from other species of thelodonts.